This project is submitted under Program Announcement (PA) Number: PAS-07-327 and Title: Early Career Award in Chemistry of Drug Abuse and Addiction (ECHEM) - NIDA (R03). Opioid-modulating peptides (Dynorphin, Nociceptin, Cholecystokinin, Neuropeptide FF) are able to both reduce and potentiate the pharmacological effects of opioids depending on their dose and site of action. Moreover, it has been proposed that these peptides are partially responsible for tolerance and dependence to classical opioid medications, which are the most frequently prescribed class of drugs for moderate to severe pain. In particular, it has been shown that the Neuropeptide FF system may act as an anti-opioid system and potentially block the development of tolerance and opioid-induced hyperalgesia. Since one of the strategies for treating drug abuse is chemotherapy, new classes of compounds are needed that could be utilized as pharmacological probes to aid in understanding the physiological mechanisms leading to drug addiction and abuse. The goal of this research project is to identify novel pharmacological probes useful for the investigation of the opioid- modulating properties of the Neuropeptide FF system. Currently, there are no small, non-peptide probes for this receptor system which greatly hampers the progress of understanding the associated physiological and biochemical roles. Our preliminary work on the design and discovery of small, non-peptidic ligands for the NPFF system has resulted in templates that have provided excellent lead compounds for further optimization. We have identified agonists and antagonists for this system but need to improve their affinities. We propose to accomplish this through the synthesis of non-peptidic NPFF1 and NPFF2 ligands as agonists or antagonists with selectivity for these receptors or a combination of affinities at each receptor. We will also perform in vitro functional assays to provide structure-activity-relationship information. It is anticipated that the outcome of this work will provide useful small, non-peptide pharmacological probes for the study of the NPFF system. Ultimately, these probes will help to define the pharmacology associated with this anti-opioid system and potentially lead to the development of novel therapeutics for opioid addicition. PUBLIC HEALTH RELEVANCE: This project is submitted under Program Announcement (PA) Number: PAS-07- 327 and Title: Early Career Award in Chemistry of Drug Abuse and Addiction (ECHEM) - NIDA (R03). Applications. We have identified two lead compounds (agonist and antagonist) for the opioid modulating system, Neuropeptide FF. Study of this proposed anti-opioid system and its role in drug abuse and addiction has been hampered due to the lack of stable, non-peptide probes for pharmacological study. Our ligands are amenable to structural modification to provide the first non-peptide probes for this system. It has been demonstrated in the literature that blockade of this endogenous system will alleviate opioid tolerance and opioid induced hyperalgesia. It is of high interest to develop probes to investigate this system to further understand these exciting pharmacological possibilities. Ultimately, these compounds (or analogs) might be able to allow for lower doses of clinically utilized opioids to lessen the chance of the development of addiction.